As a general advise of thumb, be careful to mix only enough of the adhesive to be used within 30 minutes. Using the flat side of the trowel type recommended on the adhesive package, spread a 1/4" coat on the surface of one grid area without covering the guidelines.
Make sure you use a waterproof adhesive. You can use a premixed adhesive or a mortar, but if you choose the latter, make sure it’s a thin-set variety. (Thick-bed mortars require some practice and skill at smoothing to get the tiles to sit flat, and the additional mortar isn’t necessary for a watertight finish.)

Use grout in powder and mixed with water or a recommended additive. Read the instructions on the package or ask advice at the tile store. Wear gloves and spread grout evenly, being sure to force it into the joints with a blunt stick or another tool.
One simple way to enhance your color scheme is to add a dye or pigment to the grout. White grout, even after it has been sealed with a grout sealer (which is recommended, especially for floors), may prove difficult to keep clean.

Please Make sure you sponge off the residue on the surface of the tiles before it has the chance to dry. This process will take a period of an hour or more. It’s a critical stage when you’re working with tiles that have a porous or variegated surface. Dried grout can prove almost impossible to remove from indentations.
Finally, apply a grout sealer according to the manufacturer’s directions, and your tile job is done!